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Mr. Fusion
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Mean Free Path
November 4, 2002 — 16:58

Got back from the
Hacker’s convention late last night.  Had an absolutely fantastic time. 
David Leibs roped me into talking about this project to the group, and it was
pretty fun.  I talked to a couple of real physicists about it and had a
couple of great conversations.  One was dubious of the magnetic cage
efficiently confining the electrons.  Another thought I would have to get
to 10-9 in order to get the electron and ion guns working at all. 
This is something I see as a possibility, but it doesn’t seem intuitively
correct.

The mean free path of a particle at 10-6 Torr is 50 meters. 
At 10-9, the mean free path is 50 kilometers.  The electron guns
will have only 20 to 25 centimeters path from the filament to the center of the
chamber.  Ion guns should have similar distance.  The entire chamber
is only 2.5 feet in length.  So I think the system should be at low enough
pressure to operate the guns.  The charts I’ve seen (see above) show that
10-6 is well within the range where I can operate the ion and
electron guns.  But I’ve never built nor operated an ion gun before, and
this gentleman has. 
However, I think that he was working with much larger particle accelerators than
I’m going to be.  Something I’m definitely going to be on the lookout for,
in any event.

The picture on the left is of the rapid prototyping produced disdyakis
triacontahedron cage I had made.  I had mentioned this earlier and several
people wanted to see a picture of it.  I included a handsome quarter so
that the scale would be obvious.

I’m still waiting for an official quote on the new chamber design.  It
wasn’t that much more expensive than the old design, so that’s good news. 
Well, enough for now. Gotta sleep…

Comments:
  • srivalli bose

    Can i know how you have calculated mean free path at particular pressure say 10^-11 pascals?
    please kindly reply to this question
    thank you
    srivalli bose

    March 15, 2004 — 20:18
  • There’s a good document discussing this here
    You can also find out the info in any book on vacuum engineering

    March 17, 2004 — 5:21
  • Anekwe, Emmanuel

    please Sir
    Thanks for this good work of yours in Chemistry and this topic precisely, but I’m looking a detailed record and derivation of Mean Free Path formula and its relationship in Viscosity, Thermal Conduction and diffusion. I will grateful if statistical record is also involved.
    Thanks also for the interest to help.

    March 27, 2004 — 8:24
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